This invention concerns a device for connecting and disconnecting pipes in an articulated structure level with the articulation.
Use of such articulated structures, particularly in the form of articulated tubing for underwater hydrocarbon-production operations, raises the problem of connecting the pipes inside such tubings to pipes fixed to the seabed, flexibly enough to adapt to oscillatory movements of the tubing caused by movements in the water in which it is installed.
In French patent application No. 75 11505 of Apr. 14, 1975, the applicant described a device comprising a production pipe which could move freely inside a guide-well, which itself is fixed to an articulated tubing, this production pipe containing a lower component connected on the one hand to a base pipe by means of a connection-disconnection device remote-controlled from the surface, and on the other hand to the following production pipe component by a coupling, forming a piston which can only slide lengthwise inside a cylindrical seating consisting of the lower portion of the guide-well.
In such a device, bending forces level with the articulated joint of the tubing are distributed along the lower component, which can be removed and replaced from the surface.
Such a solution is perfectly suitable for connecting pipes of small cross-sectional areas, such as pipes less than 200 mm in diameter, and particularly in an off-centre position. This is because these couplings, if they are constructed with rigid pipes, cannot respond satisfactorily to stress variations resulting from the off-centre position. However, portions of flexible pipe, consisting of concentric layers of elastic materials such a neoprene, with inserted reinforcements, possibly of metal, can be used at the tubing base in fairly axial positions to the tubing.
This invention describes a method of installing and removing these flexible pipe components for maintenance, by providing them with connection-disconnction devices at both ends.
These connection-disconnection devices, basically mechanical in nature, are used to instal or remove the flexible pipe by lowering or raising it through the pipe inside the articulated tubing, from the rig surface above the water.
In this process for connecting and disconnecting one rigid tubular pipe, referred as the tubing pipe, inside tubing connected to a base by an articulated coupling, and another rigid tubular pipe, fixed to this base and referred to as the base pipe, a flexible component to connect the tubing pipe and base pipe is lowered through the tubing pipe, at least one end of this connecting component is positioned, and each end of the component is locked in turn into the corresponding ends of the tubing pipe and base pipe, a watertight seal being provided at each end.
In this process, the length of the flexible connecting pipe between its adapter ends is less than the distance between the corresponding components at the ends of the tubing and base pipes, and one end, which contains a positioning device, is locked in position, the flexible connecting pipe is stretched, by being either pulled or pressurized, and the other end is locked in position.
In another process for connecting and disconnecting one rigid tubular pipe, referred to as the tubing pipe, inside tubing connected to a base by an articulated coupling, and another rigid tubular pipe, fixed to this base and referred to as the base pipe, a flexible component to connect the tubing pipe and base is lowered through the tubing pipe, the length of this flexible connecting pipe between a positioning device at the top and a locking device at the bottom being less than the distance between the corresponding components at the ends of the tubing and base pipes, and the upper end of the flexible connecting pipe is positioned inside the lower end of the tubing pipe, the flexible pipe is stretched by pressurizing it, and finally the lower end is locked in position inside the base pipe.
The connection-disconnection device used in this process between a rigid tubular pipe, referred to as the tubing pipe, inside tubing connected to a base by an articulated coupling, and another rigid tubular pipe fixed to this base, and referred to as the base pipe, comprises a flexible pipe with at one end an adapter containing a sealing device and a locking device, and at the other end another adapter containing a sealing device, one of these two adapters also containing a positioning device, these sealing, positioning and locking devices being designed to fit inside an upper receptacle consisting of the lower end of the tubing pipe and a lower receptacle consisting of the upper end of the base pipe, the minimum inside cross-sectional area of the upper receptacle being greater than the largest outside circumference of the flexible pipe and adapter below the positioning device on the adapter inside the upper receptacle, and the sealing device on the first adapter being positioned on the other side of the locking device from the flexible pipe.
When the second adapter contains a positioning device designed to fit into the upper receptacle, connection to the lower receptacle is obtained by pressurizing the space inside the flexible pipe.
In one embodiment, the first adapter contains a positioning device, designed to fit inside the upper receptacle.
In another embodiment, the second adapter also contains a locking device and a positioning device, the sealing devices on each adapter being located on the other side of the locking device from the flexible pipe, and the distance between reference points on the positioning devices on upper and lower adapters being approximately equal to the distance between matching reference points on the corresponding positioning devices in the upper and lower receptacles.
In one recommended embodiment, the second adapter also contains a locking device, the sealing devices on each adapter being located on the other side of the locking device from the flexible pipe, and the distance between reference points on the locking devices on upper and lower adapters being less than the distance between matching reference points on the corresponding locking devices in the upper and lower receptacles, by an amount not exceeding one quarter of the possible elastic elongation of the flexible pipe.
When the first adapter contains a positioning device designed to fit into the upper receptacle, connection to the lower receptacle is obtained by pressurizing the space inside the flexible pipe.
When the first adapter is designed to fit into the lower receptacle connection to the lower receptacle is obtained by pulling the flexible pipe upwards.
In various embodiments, the device to position an adapter inside its receptacle comprises an annular surface tapering outwards towards the top, between an upper cylindrical section and a lower cylindrical section of the adapter, and designed to rest on a tapering annular seating surface between an upper section and a lower section of the inside surface of the receptacle, the dimensions of the upper and lower sections of the receptacle being slightly greater than the corresponding upper and lower sections of the adapter.
In various embodiments, the device to lock an adapter inside its receptacle comprises an annular slot on the outside circumference of each adapter and at least one locking component, with a remote-control system on the surface which moves it from a non-locking position through an aperture in the wall of the receptacle into a locking position, both slot and aperture being at the same distance from the positioning device.
In one recommended embodiment, the system for controlling the locking movement comprises at least one cylindrical weight which moves along a cylindrical casing, on an axis parallel to the axis of the receptacle and fixed to the side of it, the weight being connected by cable with the surface, and terminating in a tapering lower end, which rests on part of the circumference of the locking component.
In this embodiment, the locking component consists of a vertical plate which can rotate freely round an axis formed by a pivot, the ends of which are fixed to the receptacle, and the lower end of the component, facing towards the inside of the receptacle, is shaped in such a way that it can rest inside the slot on the adapter, while the part of the locking component facing outwards is shaped in such a way that, whatever position the locking component is in on its axis, the tapering lower end of the cylindrical weight will rest on at least one point of it.
In one particular embodiment, the system operated from the surface to lock a lower adapter into the lower receptacle comprises an annular weight, connected to the surface by at least one operating cable, and the inside diameter of the major cylindrical part of which is greater than the largest outside diameter of the lower adapter and less than the outside diameter of a flange connecting the flexible pipe to the lower adapter, this same major cylindrical part extending downwards in a bell-shaped tapering mouth, this annular weight sliding along the lower adapter, from an initial position of readiness beneath the upper receptacle, before the connection-disconnection device is lowered, to a second position in readiness, in contact with the flange connecting the flexible pipe with the lower adapter, to a final locking position, in which the internal tapering section rests on the outer circumference of locking components, the pivots of which are positioned further down, at a distance from the axis greater than the inside radius of the ring.